1. Field of the Invention
The present invention relates to arc-welding and more specifically, to a welding flux for use in arc-welding of stainless steels.
2. Description of the Related Art
When joining stainless steel parts using arc-welding, a wide and shadow molten cavity will be seen in the stainless steel parts during welding, therefore a better welding effect can be achieved only when the thickness of the weld thickness is controlled below 3 mm. When going to joint thick stainless steel parts using arc-welding, for example, when welding a butt joint, a V-groove is made at the butt joint to shorten the weld thickness, and then welding the stainless steel parts through multiple welding procedures. This welding method wastes much time, thereby increasing the cost of the operation.
In 1960, PWI (Paton Welding Institute) disclosed a flux for arc-welding to increase the depth of weld pass penetration up to 5 mm. However, because the fluoride content produces a harmful gas to human beings during welding, this flux is not acceptable to most users. In 1996, EWI (Edison Welding Institute) developed an easy way to apply flux for increasing the penetration of gas tungsten arc-welding of stainless steel under U.S. Pat. No. 5,804,792. The flux essentially consists of reagent or laboratory grade TiO or TiO2 (about 50%), Cr2O3 (about 40%), and SiO2 (about 10%) in a liquid carrier, preferably of methyl ethyl ketone. The flux is easy to apply, increases penetration of the weld up to 5 mm. However, this composition of flux still has drawbacks. When examined the cross section of the weld pass of, for example, a butt joint, the cross section exhibited a relatively narrow middle portion and two relatively broader end portions. This problem happened due to insufficient concentration of heat energy around the two end portions of the weld pass. The uneven penetration may result in curving of the stainless steel parts during cooling. Further, when examined the outer appearance, spatters are seen around the weld pass, and a further complicated surface finishing processing process will be necessary.